S68
Brachytherapy - Gynaecology
ESTRO 2026
and more T2a-T2b (75% vs 58.4%, p=0.04) and N0 disease (46.4% vs 16.7%, p=0.02). Bladder and bowel doses were significantly lower on rescaled first- fraction dosimetry for eligible patients (Figure 1).
dose. Front Oncol. 2025 May 5;15:14076062. Li C, Li X, You J, et al. Impact of radiation source activity on short- and long-term outcomes of cervical carcinoma patients treated with high-dose-rate brachytherapy: A retrospective cohort study. Gynecol Oncol. 2020 Nov;159(2):365-372 3. Schmid MP, Fokdal L, Westerveld H, et al; GEC-ESTRO GYN Working Group. Recommendations from gynaecological (GYN) GEC- ESTRO working group – ACROP: target concept for image guided adaptive brachytherapy in primary vaginal cancer. Radiother Oncol. 2020;145:36-44 Cutting a fraction without cutting corners: dosimetric feasibility of a 3 vs 4 fraction HDR brachytherapy regimen for locally advanced cervical cancer Nikhil V Kotha, Santino Butler, Sara Richter, Thomas Niedermayr, Elizabeth Kidd Radiation Oncology, Stanford University, Stanford, USA Purpose/Objective: High-dose rate (HDR) brachytherapy for locally advanced cervical cancer (LACC) has several Mini-Oral 2575 acceptable dose-fractionation regimens contingent on tumor coverage and organ-at-risk (OAR) constraints. While 28 Gy in 4 fractions is our institutional standard given the most mature outcomes, emerging data suggest 24 Gy in 3 fractions may be comparable.1,2 However, selection criteria remain unclear. We evaluated feasibility of a 3-fraction regimen by utilizing first-fraction dosimetry from a cohort historically treated with 4 fractions. Material/Methods: Patients with LACC treated with 28Gy/4fx brachytherapy between December 2019–October 2023 were identified. Each patient’s first fraction was rescaled (without reoptimization) to 8 Gy and extrapolated to 3 identical fractions. ‘Eligibility’ for a 3- fraction regimen required meeting both guideline- concordant coverage minimum (projected HR-CTV D90 > 80Gy [EQD2]) and EMBRACE-2 OAR constraints.3 Multivariable logistic regression assessed factors associated with 3-fraction eligibility. Results: 76 patients were included (median age 49 years; 46% White/45% Hispanic; 55% FIGO 2014 IIB; 41% FIGO 2018 IIIC1). Overall, 28/76 patients (37%) met 3- fraction eligibility. Eligible and ineligible groups were similar in ECOG status, smoking history, histology, and concurrent chemotherapy. Overweight/obese by BMI criteria was more frequent in the eligible group (82.1% vs 50.0%, p<0.01). Eligible patients had smaller tumors at brachytherapy (median 20.4cc, 82% ≤ 30cc) than ineligible patients (median 30.0cc, 52% ≤ 30cc) (p<0.01)
On multivariable analysis, HR-CTV>30 cc (odds ratio 0.25, 95%CI 0.07-0.93, p=0.04) and stage T3 versus T2a (OR 0.03, 95%CI 0.01-0.49, p=0.02) were associated with decreased 3-fraction eligibility. High BMI notably increased eligibility (OR 7.30, 95%CI 1.92-27.80, p<0.01). Other variables in the final model (including % needle dose contribution; change in T score from pre- EBRT to pre-brachytherapy) were not significant (Figure 2).
Conclusion: To preserve improved outcomes afforded by brachytherapy in LACC, patient selection is key when considering 24Gy/3fx brachytherapy with a lower EQD2 than a standard 28Gy/4fx plan. Using a conservative first-fraction rescaling approach, approximately one-third of patients met 3-fraction eligibility. Although we expect higher real-time eligibility since brachytherapy leverages reoptimization and iterative fraction refinement, our study identified smaller tumor volume, lower T stage, and higher BMI as eligibility factors. Decreasing brachytherapy from 4 to 3 fractions offers several psychosocial and economic benefits for which this study provides initial criteria to consider in patient selection and evaluation with prospective studies (e.g. BRACHY-FIT: NCT07022470). Keywords: HDR Brachytherapy, Dosimetry, Patient Selection References: 1. Williamson CW, Kotha NV, Zou J, et al. Outcomes from a 3-fraction high-dose-rate brachytherapy regimen for patients with cervical cancer.
Made with FlippingBook - Share PDF online